A common problem with operating aircraft is their limited range because of fuel consumption. Aircraft such as airplanes and helicopters, both manned and unmanned, have a range limited by the amount of fuel the aircraft holds. Extending an aircraft's range requires the aircraft to carry more fuel and limits the amount of equipment or cargo the aircraft can carry. Furthermore, carrying additional fuel may require modifications to the airframe of the aircraft that impair the aerial performance of the aircraft.
The limited range of aircraft is an issue of particular importance for military aircraft. Military aircraft use specific airports for refueling and may need to carry a significant amount of equipment that limits the amount of carried fuel. Military aircraft may also need to operate over an extended range when their airframes are optimized towards other aspects of aerial performance rather than range. Extending the range or flight time of military aircraft gives to the aircraft user a competitive advantage over an adversary. For example, extending the range of military aircraft allows those aircraft to engage the adversary from longer distances, reducing the need for airbases in the range of the aircraft of the enemy. Increasing flight time reduces the cost of maintaining a complement of aircraft running, as the same aircraft can perform longer missions. Therefore, in military applications, more range is almost always a welcome capability.
The need for extended range is particularly acute when the aircraft are operating over water environments, such as oceans, seas and lakes. The watercrafts operating as mobiles aircraft bases, such as aircraft carriers or amphibious ships, carry aircraft and are high value targets for the adversary. As such, it is advantageous to position them at great distances from the forces of the adversary, therefore imposing greater needs for range for the sea-based aerial vehicles. Moreover, the water environment limits the positioning of large, land-based, tanker aircrafts close to the area of operations, because airports may not be available in that area.
Based on the above, it becomes evident that a refueling system that would be based on water vehicles and could refuel aircraft it would be useful. Watercraft can typically develop a maximum speed of up to approximately 40 knots. Therefore, if a refueling system is placed on them, the air vehicle that is being refueled will need to have the capability to fly at such a low speed.
Conventional aircraft would stall (not able to produce lift and crash) at low speeds. Therefore, a watercraft based refueling system would only be able to refuel aerial vehicles that can hover or fly at low speeds. Such aerial vehicles include the helicopters, the tilt rotor aircrafts (such as the V22) and fighters with vertical/short take-off and landing capability such as the F35B and the AV-8 Harrier. Moreover, it is advantageous for the watercraft that carries the refueling system to limit its observability by the surveillance systems of an adversary. A stealthy refueling system could remain close to the area of operations without being exposed to an adversary.
An ideal combination of such a refueling system would be a submarine that is moving at periscope depth (few meters deep; thus it retains all the innate stealth characteristics of the submarines) that refuels a F35B, a stealth aircraft. Such a combination would allow the refueling of F35Bs very close to the area of operations with a low risk of being detected by an adversary. There is a need for a watercraft based refueling system (submarines, surface ships) that would be able to refuel aerial vehicles or small sea vehicles. Furthermore, there is a need for a system that can operate “stealthily” (low observability by an adversary).